The Influence of Antioxidants on the Anti-fading Performance of Lottery Paper

With the printing and issuance of various lotteries, such as sports lotteries and welfare lotteries, the demand for lottery paper is increasing daily. Simultaneously, the improved performance of recorders places increasingly stringent requirements on thermal paper. Not only must the paper possess high color sensitivity and a wide color development temperature range of 60–120℃, but it should also exhibit resistance to water, grease, alcohol, and stains. To meet these requirements, a pre-coating is added to the base paper, effectively improving color sensitivity and image clarity. The use of a top coating (protective layer) enhances the stain resistance of the thermal paper and improves the appearance of the recording paper, effectively raising the product grade. However, the application of the top coating reduces the color sensitivity of the thermal layer to some extent. This paper applies a novel color-developing system composed of antioxidants and sensitizers to a thermal coating, evaluating the effect of the antioxidants on improving the coating's water resistance and anti-fading performance, and comparing it with two other color-developing systems.

Experimental Materials:

 Silica, hollow plastic pigment (40% solid content, average particle size 1.0 μm), carboxyl-modified styrene-butadiene latex (50% solid content, average particle size 100 nm), polyvinyl alcohol solution (10% solid content), fluorescein black dye (ODB2), benzyl paraben (PHBB, melting point 110–111℃), sensitizer, benzyl-2-naphthyl ether, antioxidant, zinc stearate emulsion, sodium hexametaphosphate (analytical grade), calcined kaolin.

Experimental Apparatus:

High-speed disperser, multi-functional paper coating machine, laboratory hot air dryer, dispersion mill, color density meter, temperature-controlled thermocouple.

Experimental Methods:

1. Coating preparation; 2. Coating and drying; 3. Thermal paper performance testing.

Conclusion:

The colorimetric system composed of a novel antioxidant and sensitizer can significantly improve the saturation color concentration of the thermal coating, achieving a saturation optical density of 1.33D.

The use of the novel antioxidant T can significantly improve the anti-fading performance of the heat-sensitive coating. After the coating has developed its color, it is immersed in water for 4 hours, and the color retention rate reaches 98.5%.